Amazon Marketplace has not sent me my phone – what can I do?

I bought a mobile phone via Amazon Marketplace in March. I have never received it and contacted the company, which informed me it uses a parcel firm for deliveries.

The delivery firm claims the phone was signed for at my address on 6 April. I live alone and wasn't in when it was delivered. Both companies are claiming they are in the right and have followed procedure but I'm still without a phone that cost £108. Can you advise what to do next? FM, Leicester

Consumer law is clear that it is the seller who is responsible for ensuring that purchases reach customers in good time and in good condition.

In this case, you are additionally protected by the Amazon "safe buying guarantee", which guarantees physical goods purchased from third party sellers. If the goods fail to arrive within three days of the maximum delivery estimate you can complain to the seller and if they haven't replied after three days Amazon will refund you. I've contacted Amazon, which has now recredited your account.

If you need help email Anna Tims at your.problems@observer.co.uk or write to Your Problems, The Observer, Kings Place, 90 York Way, London N1 9GU. Include an address and phone number.